/Engine/Source/Runtime/Slate/Public/Widgets/Layout/SSplitter.h
Resizes the children based on user input. The template parameter Orientation corresponds to the splitter being horizontal or vertical.
void HandleResizingByMousePosition ( EOrientation Orientation, const float PhysicalSplitterHandleSize, const [ESplitterResizeMode::Type](API\Runtime\Slate\Widgets\Layout\ESplitterResizeMode__Type) ResizeMode, int32 DraggedHandle, const FVector2D & LocalMousePos, [TPanelChildren](API\Runtime\SlateCore\Layout\TPanelChildren)< [FSlot](API\Runtime\Slate\Widgets\Layout\SSplitter\FSlot) > & Children, const [TArray](API\Runtime\Core\Containers\TArray)< [FLayoutGeometry](API\Runtime\SlateCore\Layout\FLayoutGeometry) > & ChildGeometries )